Session IV: Network Support for Next Generation Applications
Chair: Ibrahim Matta

This session consisted of the following three presentations, which were concerned with network services needed to effectively support next-generation applications.

Henning Schulzrinne discussed network support for adaptive multimedia applications. Henning argued that the network should provide interactive multimedia applications with not only the capability of reserving resources, but also the incentive to adapt their reservation so as to trade between blocking of their requests and the quality of service they will experience if they ask for lower reservation. To this end, Henning presented a scalable resource reservation approach, called YESSIR, that addresses the scalability problems of RSVP. YESSIR sets up reservations by having routers process RTCP messages to estimate how much resources to reserve for an RTP flow. YESSIR also implements reservation aggregation. Henning also presented RNAP, a pricing-based adapation protocol, where a service is offered at a certain price for a limited time, after which a renegotiation takes place. Both a centralized and a distributed implementation of RNAP were presented.

Bala Rajagopalan discussed practical issues in the development and deployment of constraint-based (QoS/policy) unicast and multicast routing mechanisms. Bala described the role of these mechanisms in the overall QoS framework of the Next-Generation Internet, and the current developments in the Internet protocol areas that facilitate the deployment of these mechanisms. Bala discussed the provision of VPNs and diff-serv SLAs using LSPs. For diff-serv, he pointed to the difficulties involved due to the lack of knowledge of the traffic demand matrix, which has to be estimated/measured. Bala raised several practical issues, including scalability and multicast. He presented a  flexible methodology for constraint-based routing (CBR) based on distributed overlays, where the underlying IGP is used by CBR entities to communicate.

John Zinky discussed the need for a network resource status service. This service would allow a distributed application to know the expected network performance BEFORE it starts using the resources, so that it can choose among several alternatives or know when to switch to a new alternative. John described how applications could use the service within the BBN Quality Objects (QuO) framework, which adds QoS control and measurement into CORBA. John also discussed options on how to implement such a network resource status service, and experience with several proto-type implementations, including CMU Remos.
 
 

Impact:

This session raised a number of challenging open questions that the community needs to address. First, the network, even diff-serv,  needs some form of admission control to support controlled degradation in quality for multimedia. In addition, users need economic incentives to adapt. Second, constraint-based routing has to address the practical issues of scalability, flexible deployment and measurement/estimation of traffic demands. Finally, it was felt that applications are in need for a wide-area network resource status service (a QoS layer) that measures and predicts QoS.